The invention relates generally to an accelerometer for the measurement of an axial acceleration, with sensing part consisting of an electromechanical beam, a spacer and a beam carrier and more specifically to a shock resistant accelerometer.
The knowledge of the vibrating behavior of technical structures has recently, because of its significance, obtained a special name, namely "Modal testing". The purpose of the analysis consists in creating a mathematical model of the vibrating behavior of a structure. Accelerations, as they occur for instance in connection with vibrations, are measured with accelerometers. In many cases the measurement of axial accelerations is sufficient, and it is possible to neglect the angular accelerations. The measurement of axial acceleration is achieved by fastening the accelerometer at the surface of the object to be measured, either by screwing or by gluing. An accelerometer already introduced in practice has a sensing part consisting of a pair of electromechanical sections of beam with equal dimensions, arranged symmetrically to a main axis, a spacer and a beam carrier. The spacer is situated in this main axis and is connected with the sections of the beam at one end and with the beam carrier at the other end. The beam carrier lies on two opposite steps of the housing and is solidly fixed. Thus the sensing part, consisting of the two sections of the beam, the spacer and the beam carrier, is formed as a suspension construction. Accelerometers for the measurement of an axial acceleration of this kind are already commercially available.
The theory of "Modal testing" is described for instance in the book "Modal Testing, Theory and Practice", by D. E. Ewins, Research Study Press Ltd., 1984, on pages 87-152.
An important disadvantage of the already commercially available accelerometers is the fragility of the sensing part. By mounting or dismounting a measuring instrument, it is often dropped on the floor and the sensible sensing part breaks.
Thus it is an object of the invention to create an accelerometer with improved shock resistance. According to the invention, this objective is reached by making the two sections of the beam of unequal length. Furthermore the shock resistance can be improved by appropriate dimensions of the beam and convenient fastening of the spacer at the beam.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjuction with the accompanying drawings.